Mornin, Treeman!
I wasn't there on the day you mention, but have photographed many an "orb" in my time...
Being a fan of holy wells, I notice that these appear, in my experience, in the more "active" of wells and springs...
I have a photo of St Nectan's Glen, which, when I first saw it, I was quite freaked out! Loads of these "orbs" and nothing else! Some appeared to have faces in!
When I came doen to earth, I realised that they were merely water droplets in the air, being caught by the camera's flash. Bah! I sort of hoped that there was a LESS simple explanation, and it may not be the case in all instances (I've seen moving ones on film before), but in my humble one, that is what they are. Bah, again!
G x